Generators normally comprise a rotor and a stator, the rotor being arranged rotatably relative to the stator with a small air gap there between. It is necessary to achieve and maintain a high precision in the air gap between the rotor and the stator since the air gap, also for very large generators, has to be quite small, and generally only a few millimeters. To this end the rotor and the stator have previously been designed very rigid and heavy.
US 2010/0007225 A1 discloses a generator or motor apparatus having a stator formed from a plurality of pairs of parallel stator segments. The pairs of parallel segments are connected together to form a channel in which an annular rotor moves. The annular rotor also comprises a plurality of detachable segments connected together to form an annular tram operable to move through the channel. Each stator segment comprises a stator winding set, and each rotor segment comprises a magnet dimensioned to fit between the parallel spaced apart stator segments. Variations in AC outputs may be minimised by connecting stator segments in parallel to each other. As a given rotor segment passes the stator segments of a given pair, any mechanical deviation from centre in which the given rotor segment is distant from one stator segment of the given pair is matched by the given rotor segment being correspondingly closer to the other stator segment of the given pair.